The invention relates generally to apparatus for reading codes on containers and deals more particularly with apparatus for optically reading relieved code elements.
Codes are widely used today on various products to provide source, pricing and other information about the product. For example, in the bottle making industry, bottles are often formed by a multiple section forming machine, and a code is molded into each bottle indicating the section in which the bottle was formed. In the event that a particular mold produces defective bottles, the defective bottles can be detected by inspection apparatus and the mold code of the defective bottles read to determine the source of the defective bottles. At which time, the defective mold may be replaced.
The molded code may take various forms such as a bar code, a dot code or a ring code, which bars, dots or rings may protrude from the bottle sidewall or bottom surface. In U.S. Pat. No. 4,524,270 to Martin, a bar code reader is disclosed. The U.S. Pat. No. 4,524,270 issued June 18, 1985 is assigned to the assignee of the present invention and is hereby incorporated by reference as part of the present disclosure. The 4,524,270 optical reading head is positioned at the level of the code. Each of the bar code elements protrudes from and is skew relative to the surface of the surrounding region of the sidewall and the bottle is rotated to sequentially expose each bar code element to the scanning head. The scanning head comprises a source of light aimed at the level of the code, a linear array of optical receiving fibers, a lens assembly positioned to receive light reflected from the code elements and focus the light onto the linear array of optical fibers and a series of photosensitive diodes associated with each of the optical fibers, respectively. When each bar passes in front of the scanning head, light reflects from the surface of the bar through the lens assembly and into one or more of the receiving optical fibers to indicate the presence and length of the bar. When a region of the sidewall surface is exposed to the scanning head and no code elements are present, then the light source illuminates the sidewall and the light is reflected away from the lens assembly and no diodes are activated.
It has proven difficult in practice to produce the code elements with enough precision and to align the code elements with the lens assembly and receiver fibers with enough accuracy to ensure that light reflected from the reflective surface of each code element actually reflects through the lens assembly and into the linear array of receiver optical fibers. Without such precision and alignment, it is difficult to detect the bar code elements. In addition, occasionally the scanning head, even when properly aligned with a code element, detects reflections from a back side of the bar code element, a so-called "phantom" reflection, which further complicates the code reading process.
Dot code elements take various forms such as rounded wedges as disclosed in U.S. Pat. No. 3,991,883 to Hobler et al, which patent is hereby incorporated by reference as part of the present disclosure, and raised hemispherical "bumps". In the past, such codes have been detected by projecting light onto each dot in sequence and positioning a photodetector to receive a reflection from the dot in a similar manner to the detection of bars discussed above.
U.S. Pat. No. 4,201,338 to Keller discloses a dot code formation having two parallel, linear patterns of dots. One pattern comprises equally spaced dots and serves as timing marks, and the other pattern contains dots aligned with some of the timing dots and contains the actual binary information of the code. The 4,201,338 patent also discloses a light source positioned to transmit light horizontally approximately tangent to a container sidewall, and a photodetector positioned to receive light reflected at approximately 70.degree. relative to the angle of the incident light, which photodetector is positioned approximately normal to the tangent point. The positioning of the photodetector corresponds to the angle of light reflected from the dots.
Another previously known dot formation has a single linear pattern of dots, two dots at the beginning spaced by a standard amount, two dots at the end spaced by a standard amount and five other dots between the beginning and end pairs of dots. Between the beginning and end pairs of dots is a linear distance sufficient to contain nine dots based on the aforesaid standard spacing. The dots at the beginning and end serve to frame the code, and the location of the five intermediary dots provides the actual information.
Accordingly, a general object of the present invention is to provide an apparatus for reading molded and other relieved code elements, which apparatus does not require precise alignment with the code elements or strict manufacture tolerances in the code elements.